Sizing composition and glass fibers treated therewith

ABSTRACT

A sizing for glass fibers, comprising water soluble epoxy resins, an organosilane, polyvinyl acetate copolymer and a lubricant is provided, whereby the sized glass fibers in the form of strands possess excellent integrity.

United States Patent Ward 5] Mar. 28, 1972 [54] SIZING COMPOSITION ANDGLASS [56] References Cited FIBER TRE TE T S A D HEREWITH UNITED STATESPATENTS [72] Invent: wardnoughmMlch' 3,459,585 8/1969 Killmeyer et a1...1 17/126 GE [73] Assignee: Owens-Corning Fiberglas Corporation PrimaryExaminer-William D. Martin [22] Flled: 1970 Assistant ExaminerD. Cohen[21] APPLNO'; 25,584 Attorney-Staclin8z0verman [57] ABSTRACT [52]U.S.CI. ..ll7/126 GE,117/4,216lg//8l365 A Sizing for glass fiberscomprising water Soluble p y I Cl C03 25 02 resins, an organosilane,polyvinyl acetate copolymer and a [51] nt. c lubricant is provided,whereby the Sized glass fibers in the [58] Field of Search ..1 17/126GE, 126 GB, 161 ZB, form ofstrands possess excellent integrity.

4 Claims, No Drawings SIZING COMPOSITION AND GLASS FIBERS TREATEDTHEREWITH BACKGROUND OF THE INVENTION This invention relates to glassstructures such as glass fibers in which the surface characteristics ofthe glass structure have been modified to enable the glass fibers, instrand form, to be chopped without losing their integrity, whilepossessing other favorable characteristics. Some of the other favorablecharacteristics possessed by the chopped strands include: flowability ofthe chopped strands during processing, mixing, handling, conveying andmolding within a resinous matrix; low bulk density; heat resistance;lightness of color; and the chopped strands impart high impact strengthsto resinous matrices due to a strong bonding relationship between thesized chopped strands and the resinous materials, whether thermoset orthermoplastic.

Difficulties in the establishment of a chopped glass strand thatpossesses integrity during processing, flowability during processing,lightness in color and which imparts high impact strengths to resinousmatrices are well known in the art.

From the time of formation of glass fibers to the more distant point intime of their incorporation into a resin matrix to reinforce the same,many processing operations will have had to be carried out. Immediatelyafter the glass fibers are formed and traveling at linear speeds inexcess of 10,000 ft./min. a protective coating is applied to the glassfibers to prevent mutual abrasion. Subsequently, the sized fibers aregathered onto a rotating collection package or routed directly to achopping apparatus where the glass strands are chopped into lengthsranging from one-eighth to three-eighth inches.

When the strands are gathered onto a package it is preferable to dry thepackage prior to positioning the package on a creel with numerous otherpackages, so that a plurality of sized strands may be subsequently fedto a chopping machine. When the strands are fed directly to the chopper,the drying may be prior to or subsequent to chopping. When the strandsare dried prior to being chopped a less integral strand results whereaswhen the strands are chopped subsequent to chopping a highly integralstrand results. Because of the differences in integrity the amount ofsolids of the sizing on the glass fibers may be adjusted accordingly tocompensate therefor.

Subsequent to chopping, the chopped strands may be either packaged for alater use or be combined and mixed with a resinous material to form apremix which is used as a molding compound. Finally the molding compoundmay be either packaged for subsequent use or may be immediately used ina molding operation to form reinforced articles.

The treatment applied to the glass fibers at forming must bemultifunctional for the purposes of this invention. It must be capableof protecting the individual fibers from mutual abrasion, capable ofholding the strand in an integral unit before, during, and afterchopping, capable of exhibiting antistatic characteristics so thatduring handling, conveying, mixing and molding, the chopped strands haveflowability and capable of a strong bonding relationship with a resinousmatrix that is to be reinforced.

Difficulties in the establishment of a strong and permanent bondingrelationship between the surfaces of glass fibers and a and the like,penetration of resinous materials into the fibers is not available foruse in establishing a bonding relationship between such glass fibers anda resinous material. Because glass fibers naturally form into elongaterods having very smooth surfaces, as distinguished from the roughsurface characteristics of natural fibers, a gripping relationship or amechanical bonding is difficult to establish between resinous materialsand the untreated glass fiber surfaces. Thus a physical anchorage of thetype relied upon chiefly for the establishment of a bonding relationshipbetween natural fibers and resinous materials is not capable of beingdeveloped with glass fibers. Glass fibers may be etched or roughened topresent a surface of some porosity but desirable strengthcharacteristics of the glass surfaces are simultaneously lost.

In the absence of the ability to make use of physical forces in bonding,it becomes necessary to rely upon the development of a relationshiprequiring chemical bonding or physical chemical forces based uponmolecular or ionic attraction and the like. With synthetic resinousfibers, e.g., nylon, polyester, etc., a strong bonding relationship canbe developed with the smooth surfaces because such fibrous materials areresinophilic in character and therefore are preferentially receptive toresinous treating materials. In addition, the resinous materials, ofwhich the fibers are formed, have the ability of being softened by heator solvent in a manner to enable the development of a desired bondingrelationship with the applied treating material. Such chemical forcesresulting from the softening of the synthetic fiber surfaces are notavailable with glass fibers because the glass fibers are inert to heatand solvents and because the glass fiber surfaces are dominated bygroups that are hydrophilic in character and therefore receive moisturein preference to resinous materials. As a result, only a weak bondingrelationship is capable of being established in the first instance andeven this limited bonding is reduced in the presence of moisture or highhumidity sufficient to cause a moisture film to form and separate theresinous coating from the glass fiber surfaces with a moistureinterface.

When a strong bonding relationship cannot be established between glassfibers and a resinous material used in combination therewith, maximumutilization of the strength properties of the glass fibers cannot bemade available in the products that are formed. Even where a fairbonding relationship between glass and resin can be established underextremely dry conditions, the strength properties of the glass fiberreinforced plastic composite depreciates greatly under high humidityconditions or in the presence of moisture.

When glass fibers are formed into strands, containing many fibers, andthe strands are subsequently chopped into lengths of from aboutone-eighth inch to about three-eighth inch, it is desirable to have thechopped strand possess integrity. That is, after chopping it is desiredto have the strand in a rod-like manner without the many fibers makingup the strand separating from the rod-like structure. The desirabilityof this rod-like structure is important when a resinous matrix is to bereinforced with glass fibers to improve strength and othercharacteristics. Another desirable characteristic of the chopped strandsof this invention is that they have a high degree of flowability duringprocessing, especially within the resin matrix that is to be reinforcedso that the chopped strands have a uniform dispersement within thematrix and not be heavily grouped in one local concentration and void ofchopped strands in another concentration.

It is therefore an object of this invention to produce a treatment forglass fibers and to produce glass fibers treated with a material toenable the glass fibers, in strand form, to be chopped without losingtheir integrity during processing.

It is another object of the invention to provide a new and improvedcoating for glass fibers so that the coated fibers, when gathered into astrand, chopped, and subsequently used as a chopped reinforcement inresinous matrices, remain flexible and substantially insoluble in thematrices.

It is another object to produce glass fibers, which when chopped,possess good flowability characteristics during processing.

It is still another object to produce glass fibers, which whenincorporated with a resinous matrix, exhibits a strong bonding chopper.It is desirable to obtain chopped strands of uniform length, but thisbecomes difficult when the chopper becomes clogged with previouslychopped fibers. Static forces are set up on chopping and must becombated.

The lack of strand integrity during processing is more than a problem.It is detrimental to the uniform distribution of chopped strands withina resinous matrix because the strands agglomerate or clump together.When a thermosetting matrix is to be reinforced, a premix, comprisingthe chopped strands and the resin, is formed. When a thermoplasticmatrix is to be reinforced, the chopped strands and resin are introducedinto an injection molding machine as a dry blend via vibration. Iffilamentation of the chopped strands occurs, the strands will tend tostick together through physical or static forces, and cause anon-uniform distribution of the strands into the matrix,.or anon-uniform distribution of the strands into the injection moldingmachine.

The degree of integrity possessed by the chopped strands becomesextremely important when the strands are incorporated with a resinousmatrix. During the incorporation it is desirable to obtain somefilamentizing of the strand sufficient to increase the surface area ofavailable reinforcement, but insufficient to be incapable of actualreinforcement. it has been found that when the strands have no degree offilamentation upon incorporation with a resinous material, strengths ofthe composite are low. The same phenomenon is present when there is nointegrity of the chopped strand after incorporation of the' strand withthe resinous matrix. Therefore, a compromise between a highly integratedstrand and a highly filamentized strand must be reached. Chemical aswell as physical forces contribute to the degree of filamentation of thetreated strand, after incorporation into a resinous matrix.

The inventive treatment, hereinafter described in greater detail,provides all of the advantages as above described.

SUMMARY OF THE INVENTION According to the present invention it has beendiscovered that impact strengths of resinous matrices reinforced byshort lengths of glass fibers are greatly increased if the short lengthof fibers are in the form of a strand having some degree offilamentation, rather than dispersed throughout the resin as individualfilaments or small groups of filaments. The inventive treatment whichbonds the fibers together into a strand is of low or intermediatemolecular weight, so that it is flexible, but is crosslinked to arelatively insoluble degree and capable of holding the fibers togetherin the form of a strand during processing. Residual reactivity of thetreatment provides a controlled bonding between the treatment on thestrands and the matrix resin.

According to the invention, the film former within the treatment iscapable of partial reaction during the fiber forming operation to forman integral strand and it is capable of further reaction whenincorporated in a resinous matrix, to provide a controlled degree ofattachment between the surface of the fibers and the matrix resin. Thecoating on the fibers is generally immobile or in a solid state, and thedegree of bonding which is achieved between the strand coating and thematrix resin is a limited or controlled one, which allows the bondbetween the strand and the matrix resin to yield under a concentratedload, such as occurs during impact. Concentrated loads cause some ofthese bonds to be broken to allow the strand to move. It appears thatsome degree of filamentation of the treated strand is necessary uponincorporation of the strand with the resin matrix so that a synergisticsystem is developed.

In a preferred form of the invention, individual glass fibers are coatedat forming with a water dispersion comprising a low or intermediatemolecular weight polyvinyl acetate copolymer, a metal acid catalyst, anda combination of epoxy resins modified to act as lubricants. After theindividual fibers are coated with the dispersion, they are gatheredtogether into a strand and collected on a package and dried at atemperature which causes the polyvinyl acetate copolymer to crosslink.The crosslinking of the polyvinyl acetate copolymer causes the coatingto set up sufficiently, so that it is flexible but substantiallyinsoluble in a solution of matrix resin. The matrix resin may be astyrene solution of a crosslinking polyester resin, or may be an organicsolution of some other unsaturate such as polypropylene, polyethylene,or polystyrene. When the coated strand is mixed with the matrix resinand cured at a temperature above the drying temperature employed atforming to crosslink the coating material, a polymerization of thematrix resin is produced, and a limited number of bonds are formedbetween the surface of the strand coating and the matrix resin. Thelimited number of bonds between the solid coating material and thematrix resin becomes sequentially broken when subjected to concentratedloads, to allow a yielding of the matrix resin relative to the strand,and a consequent redistribution of the load over a number of strands. Inaddition, the coated strands are locked into the resin matrixmechanically upon polymerization of the resin matrix. A considerableimprovement in impact strength is thereby produced.

The metal acid catalyst or Lewis Acid is selected from a general classof soluble metal salts of the transition metals. These include aluminum,calcium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel,copper, zinc and strontium. Metal chlorides such as AlCl and metalnitrates are the preferred metal salts.

DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLE I A sizing compositioncomprising an aqueous dispersion of the following materials is preparedas follows:

Material Percent by weight Epoxy A 0.l -2.0 (active solids) Epoxy B 0.13.0 (active solids) Epoxy C 0.! 2.0 (active solids) Glacial acetic acid0.] -0.5

Paintable silicon fluid emulsion 0.1 -l.0

Gamma glycidoxypropyltrimethoxysilane 0.05 -0.8

Polyvinyl acetate copolymer 3.0 -l0.0 (active solids) Ionic solution ofMCI, 0.06 -0.36 (active solids) Deionized Water Balance The pH of thefinished size should be from 4.0 to

about 5.0.

The pH of the dispersion should be approximately 4.5.

The materials were mixed together by combining acetic acid with epoxiesA, B, and C. The resinous mixture was heated to l20140 F. and then cool,deionized water (45-6 5 F.) was added slowly to the heated mixture withthorough and vigorous agitation (Lightnin mixer is suitable) until theresinous mixture inverts from a slightly viscous to a highly viscousstate. Upon inversion, an additional gallon of water is added. Thismixture is agitated for about 10 minutes and further diluted with 20gallons of water. Subsequently, polyvi- I nyl acetate copolymer, AlClgamma glycidoxypropyltrimethoxysilane and the paintable silicon fluidemulsion are added to the mixture. Additional water is added in order toadjust the solids of the mixture from about 6.0 to about 12.0 percent.

d The vessel is suitably closed off, and is provided with a refluxcondenser to prevent the escape of solvents and/0r heated to 105 C. withstirring to thoroughly dissolve the resin and thereafter the temperatureis raised to 120 C. and approximately 65 parts by weight diethanolamineis added slowly with continuous mixing. The products are held atapproximately 120 C. for about 1 hour to provide ample time to react allof the amine. The material produced by the above reaction is essentiallythat of Structure ll shown before, and contains a preponderance ofmolecules having a single terminal solubilizing group at one end.

Thereafter a polyglycol monoester, such as a polyglycol monooleate, isadded and reacted with the remaining oxirane groups. Approximately 400parts by weight of a commercially available polyethyleneglycolmonooleate having a molecular weight of about 400 is added to thereaction kettle using about 2.5 parts by weight of a basic catalyst (asfor example potassium carbonate), and the mixture heated to maintain 120C. for 4 hours. The resulting material has an epoxy equivalent of 3,000,indicating one epoxy equivalent for 3,000 gm. of the material. Thematerial produced by the above reaction is shown by the followingformula showing the preponderance of molecules that have terminalsolubilizing groups at both end 9f the molecule:

reactants. Approximately 64 parts by weight of diethanolamine is addedwith mixing. The temperature is raised to 100 C. with continuous mixingand held at 100 C. for 1 hour to provide ample time to react all of theamine. The material produced by the above reaction was essentially thatindicated by the following formula, having a single terminalsolubilizing group at one end:

Epoxy B This material is prepared by dissolving approximately 805 partsby weight of the general type of epoxide indicated by Structure I havingan n of about 3.6, with 345 parts by weight of xylene in a 2-liter Kimaxreactor kettle having a motor driven agitator therein and surrounded bya Glas Col heated mantle controlled by a Variac. The vessel is suitablyclosed off, and is provided with a reflux condenser to prevent theescape of solvents and/or reactants. The mixture is wherein x 8 to 10Epoxy C This material is prepared by dissolving approximately 530 partsby weight of the general type of epoxide indicated by Structure 1 havingan n" of about 3.6 with 390 parts of xylene in a 3-liter Pyrex reactorkettle having a motor driven agitator therein and surrounded by a GlasCol heated mantle controlled by a Variac. The vessel is suitably closedoff, and is provided with a reflux condenser to prevent the escape ofsolvents and/or reactants. The mixture is heated to 105 C. with stirringto thoroughly dissolve the resin, and thereafter the temperature israised to 120 C. and approximately 43 parts by weight of diethanolamineis added slowly with continuous mixing. The products are held atapproximately 120 C. for about 1 hour to provide ample time to react allof the amine. The material produced by the above reaction is essentiallythat of Structure ll shown before, and contains a preponderance ofmolecules having a single terminal solubilizing group at one end.

Thereafter a polyglycol monoester, such as a polyglycol monooleate, isadded and reacted with the remaining oxirane groups. Approximately 720parts by weight of a commercially available polyethyleneglycolmonooleate having a molecular weight of about 1,500 is added to thereaction kettle using 5 about 2.5 parts by weight of a basic catalyst(for example potassium carbonate) and the mixture heated to maintain 120C. for 4 hours. The reaction vessel is cooled to about 200 F. and about100 parts of diacetone alcohol or other polar solvent is added and thissolution stirred while cooling to room temperature. The materialproduced by the above reac tion is shown by the formula showing thepreponderance of molecules that have terminal solubilizing groups atboth ends 2f the molecule:

whereinx =28 to 36.

w The paintable silicon fluid emulsion is commercially availableunder-the trade name SM-2050 from General Electric Company. Thegamma-glycidoxypropyltrirnethoxysilane is commercially available underthe trade names A-l87 and Z- 6020 from Union Carbide Corporation andDow-Coming Corporation respectively. The polyvinyl acetate:N-methylolacrylamide copolymer emulsion is commercially available under thedesignation -2828 from National Starch Company. The AlCl is commerciallyavailable under the designation 42-2301 from National Starch Company.

Eight hundred sixteen continuous filament glass fibers approximately0.00050 inch in diameter were produced by attenuating molten streams ofglass at a rate of approximately 10,000 feet per minute. The glassfibers, immediately after solidification, were pulled over a graphiteapplicator that was; flooded with the aqueous dispersion given above.The coated fibers were brought together into a strand by the applicator,and the strand was then wound on a rotating drum mounted on a revolvingspindle which pulled the fibers at a rate of approximately 10,000 feetper minute. A suitable traverse mechanism moved the strand back andforth across the drum to'produce a coiled package approximately 12inches wide, with an inside diameter of approximately 8 inches, anoutside diameter of approximately 12 inches, and tapered sides. Thepackage was removed from the spindle and dried in an oven at atemperature of about 265 F. for approximately 8 to 20 hours. Thereafterthe strand was unwound from the package and chopped into one quarterinch lengths.

A matrix resin mix was made from the following ingredients:

Ingredients Parts by Weight Unsaturated polyester resin (1 mol phthaliclnhydride, l mu] maleic anhydride, 2 mols i propylene glycol cooked toan acid number of -35 and diluted with 30% styrene solvent) 20] 1.0Tertiary Butyl Perbenzoate 13.2 Benzoyl Peroxide 6.0 Zinc Stearnte 80.0

. The resin mix was produced by charging the polyester resin to a cowlesmixer, and thereafter slowly adding the other ingredients while themixer was running to thoroughly disperse the ingredients throughout theresin.

A Molding Premix was made from the following ingredients:

Ingredients Parts by Weight Above resin mix 1763.0 Calcium Carbonate 325mesh filter 315.0 Clsy filler 2832.0 56 inch chopped strands given above(98 percent glass) 1080.0

tough, hard coating on the glass fiber strands that possesses aBaker-Perkinssigma blade type mixer, and adding the clay.

The Molding Premix was made by adding the resin mix to a and thecalciumcarbonate fillers while the mixer was running;

After the above ingredients were dispersed in the resin, the

mixer was run for an additional 6-8 minutes to assure a uniformdispersion. Thereafter, the quarter inch chopped strands were blended induring a 30-second period, and the mixer was run for an additional l/i-minute period to assure a uniform dispersion of the strand throughoutthe mixture of other ingredients. The chopped strands showed a slightdegree of filamentation after mixing, which is a desirablecharacteristic of glass strands treated according to the inventive concet.

he chemically reactive polyvinyl acetate copolymer undergoes a highdegree of crosslinking thereby producing a highly insolublecharacteristic with a resinous matrix. The in-. solubilitycharacteristic becomes extremely important when preparing a premixcompound and/or when an injection molding machine is used, because itcontrols the degree of filamentation of glass filaments from the strandinto a multiplicity of discreet bundles, smaller in diameter than theoriginal strand. Some filamentation is desirable but too much or toolittle is undesirable. This desirability has been proven by conductingimpact tests upon the reinforced structures. Analysis shows that impactstrengths are greatest when there is some degree of filamentation of theglass filaments from the strand.

In addition to the chemically reactive polyvinyl acetate copolymer, thecombination of special epoxy resins, used in strand during drying butprevents crosslinking of the coating from strand to strand on theforming package. Without this lubricity characteristic, there is aslight strand-to-strand bonding on the package, sufficient in strengththat upon removal of the strand from the package, the strand separatesfrom itself thereby destroying its integrity, and furthermore causesfuzzing and broken strands. When the integrity of the strand isdestroyed, the advancing strand at the chopper tends to foul the chopperthereby cutting down on the chopper efficiency and the uniformity of thelength of chopped strands.

I claim:

1. Glass fiber strands having a dried coating of a sizing com- P on mp iin rersmt z Ws s la- Epoxy A, having the following formula: 0.1-2.0(active solids) wherein 12: about 3.6

wherein x=8 to 10 and wherein n=about 3.6

Epoxy C, having the following formula:. 0.1-2.0 (active solids)HO--CHz-CHI wherein z=28 to 36, and wherein n=about 3.6 W.

- Glacial acetic acid 0.! --0.5 Glacial acetic acid 0.16 Paintablesilicon fluid emulsion 1 5 Painlable silicon fluid emulsion 0.30 Gammaglycidoxypropyltrimelhoxysilang 5 3 Gamma glycidoxyprcpyltrirnethoxysilane 0.40 I Polyvinyl acetate :N-methylol acrylamide copolymer 3.0-l0.0(active Poly l' Reta iN-methylol acrylamlde l l' f solids) so 1 s) IIonic solution of Alcl (1064136 (active lomc solution ofAlCl, 0.()active SO! 5 sends) Deionized water Balance Deionized water Balance 2.Chopped glass strands having the dried coating as 4. Chopped glassstrands having the dried coating as claimed in claim 1. i'claimed inclaim 3 wherein the chopped glass strands possess 3. Glass fiber strandshaving a dried coating of a sizing cornsubstantial integrity. positioncomprising in percent by weight: a

Epoxy A, having the following formula: 0.38 (active solids) 311 CH;HOCH:CI: (I)H OH N-CH1CHCHrO -o-0H,-oH-om- HO-CH CH a CH3 CH3 whereinn=about 3.6

Epoxy B, having the following formula: 1.07 (active solids) OH; 013 ECH:H-CH9[OCH1CH2] O- (CHz)1-CH=CH(CHa)1- Ha wherein 1 8 to 10, andwherein n about 3.6

Epoxy C, having the following formula: 0.19 (active solids) CH; CH,HOCH:CH1 on I OH NCH;CHCH;- -ooHr-oH-cHi HO-CH CH1 CH3 L CH3 OH 6CH,-HCH1T :OCHzOH1}OC(CH:)nC-Hz wherein z=28 to 36, and wherein n=ab0ut3.6

2. Chopped glass strands having the dried coating as claimed in claim 1.3. Glass fiber strands having a dried coating of a sizing compositioncomprising in percent by weight:
 4. Chopped glass strands having thedried coating as claimed in claim 3 wherein the chopped glass strandspossess substantial integrity.